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  1. #1
    Join Date
    Jan 2007
    Location
    Rosetown, SK.
    Posts
    519

    Default Proper way to mount electrical box on weld table.

    Always wanted to mount a plug in box ( 110 ) on my welding table. Can someone telll me the safe proper way to do it. It will be fed by a cord from a wall outlet. Do you want the box isolated so welder ground can not backfeed to 110 or how. Thanks in advance for your input.

  2. #2
    Join Date
    Dec 2007
    Posts
    157

    Default

    I would isolate (insulate) the box from the welding table. You want the path of least resistance to be between the work clamp and the electrode; completing the circuit as directly as possible. You do not want that path or part of it to inadvertently be between the electrode and the relatively light gauge wire in the outlet cord.

    The other issue is electromagnetic interference. The less isolated the welding circuit, the more conductors to generate interference.

    Make sure that the cord includes a ground wire which connects directly to the green ground screw on the receptacle(s). If you use a metal box, I would loop the green ground to a ground screw on the box as well. This way if you somehow short on to the box, or a tool that is plugged into the receptacle shorts, the ground wire disapates the load instead of you.

    Here, (Chicago area) everything is in emt or metalic conduit, but I still like to add the ground to the outlets & box for receptacles set up in a shop. You never have to worry about a fitting or set screw being loose. Take special care in areas where everything is in Romex and/or other non metalic conduit and boxes as faulty grounding is common.

    Of course all that is for nothing, if the outlet that you plug into does not have a proper ground. I would again run a ground wire from the receptacle and the box and in this case back to the distribution panel and to the ground bus. You are only as grounded as what you are pluged into.

    This way you are assured that you always have a proper continuous ground.

    A couple of other things. Use a gfi as added protection, especially if it is in a damp/wet area (code here for any garage). You can also use plastic outlet strip (cheap & disposable) and you can mount it without grounding worries. Another thing you can do is have a short lead for the table receptacle that you plug into the appropriate extension cord. That way when the cord is in the way or is not needed you dont have it rolled up at the table. I rig up temp panels for construction sites like that and use twist lock plugs & receptacles (expensive!) so that it does not easily unplug. Of course then you have to make a special cord.

    I'm not an electrician, but I am a general contractor and deal with all sorts of issues from single receptacles to services. I have seen too many dangerous set ups. Be Safe! I hope this helps.

    John

  3. #3

    Default

    I would use a pvc box when mounting on a welding table and put a springloaded weatherproof cover on it to keep grinding dust and sparks out of it when something isnt plugged into it. With a metal box you run the risk of the welding path going down the grounding wire of the receptacle wiring if you loose your grounding/work clamp off your table or work. Seen it happen many times(30 years in electrical trade). The cable from the work table to what ever receptacle you have it plugged into will melt in short order with and possibly damage the wire all the way back to your panel. 100 amps going down that little wire creates a lot of heat. There are no fuses on a ground wire to limit the current. That can be expensive to replace and a big fire hazard also.
    Last edited by WolfmanJack13; 02-15-2008 at 09:47 AM.

  4. #4

    Default

    Quote Originally Posted by WolfmanJack13 View Post
    I would use a pvc box when mounting on a welding table and put a springloaded weatherproof cover on it to keep grinding dust and sparks out of it when something isnt plugged into it. With a metal box you run the risk of the welding path going down the grounding wire of the receptacle wiring if you loose your grounding/work clamp off your table or work. Seen it happen many times(30 years in electrical trade). The cable from the work table to what ever receptacle you have it plugged into will melt in short order with and possibly damage the wire all the way back to your panel. 100 amps going down that little wire creates a lot of heat. There are no fuses on a ground wire to limit the current. That can be expensive to replace and a big fire hazard also.
    This is a good idea. I was trying to figure out how he was going to attach a metal box to the table without it interfering with the ground.

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